Polyolefin resin film and laminate using the same

Abstract

Provided is a polyolefin resin film such that, when laminated with a substrate film having large distortion of the molecular orientation axis, such as a biaxially stretched polyamide resin film, a packaging pouch obtained from said laminate has excellent transparency, heat seal properties, straight-line cuttability, tearing properties, pouch-making properties and pouch rip resistance, and is not susceptible to forming tufts when opening.　A polyolefin resin film comprising a polypropylene resin composition, wherein: 100 parts by weight of the polypropylene resin composition contains 20-95 parts by weight of a propylene-α olefin random copolymer containing a metallocene olefin polymerization catalyst, 0-75 parts by weight of a propylene-α olefin random copolymer containing a Ziegler-Natta olefin polymerization catalyst, and 5-15 parts by weight of at least one elastomer selected from the group consisting of ethylene-butene copolymer elastomers, propylene-butene copolymer elastomers, and ethlene-propylene copolymer elastomers; the heat shrinkage in the larger amongst the length direction and the width direction of the polyolefin resin film is 1-10%; and the x-axis orientation factor ΔNx calculated from the refractive index of the polyolefin resin film is 0.0130-0.0250.

Description

[Technical Field]

[0001] The present invention relates to a polyolefin resin film and a laminate thereof with at least one substrate film selected from the group consisting of a polyamide resin film, a polyester resin film, and a polypropylene resin film. [Background technology]

[0002] Packaging bags are manufactured by heat-sealing (hereinafter referred to as heat sealing) the periphery of a laminate of a base film, such as a polyamide resin film, polyester resin film, or polypropylene resin film, and a polyolefin resin film, with the polyolefin resin film surfaces in contact with each other at a temperature close to the melting point of the polyolefin resin film. Semi-retort pouches, which are food packaging bags that are filled with food and then sterilized with pressurized steam at around 100°C, are widely used and are suitable for storing food for long periods of time. In recent years, due to social factors such as the increasing participation of women in the workforce, the trend toward nuclear families, and the aging of the population, demand for semi-retort pouches, as well as retort pouches, has been increasing, and at the same time, there is a demand for further improvement in their properties. For example, in recent years, these semi-retort pouches are often packed in boxes, transported, and sold in stores, so they are required to be resistant to tearing even if dropped during this process, particularly when dropped under refrigeration.

[0003] Furthermore, when removing food contents from a packaging bag, particularly a semi-retort pouch, the packaging bag is often torn by hand from a slit made in the heat-sealed portion around the periphery of the bag, known as a notch. However, when a conventional laminate is used, the bag cannot be torn parallel to one side, which is usually the horizontal direction, and the bag ends up being opened at an angle, or the tearing direction of the laminate on the front and back of the packaging bag is reversed on the top and bottom, a phenomenon known as tear separation, occurs, making it difficult to remove the food contents and posing a risk of staining hands and clothes with the food contents, or of causing burns if the contents are heated.

[0004] The reason why it is difficult to tear a packaging bag parallel to one side of the packaging bag is that the base film used in the laminate is distorted, i.e., the molecular orientation axis direction of the base film is not parallel to one side of the packaging body.

[0005] This problem would not occur if the molecular orientation axis direction of the base film could be made the same as the tear direction of the packaging bag. The molecular orientation axis direction of the produced wide-width stretched film in the widthwise center portion is aligned with the running direction of the film, making it possible to tear the packaging bag parallel to one side. However, at the widthwise ends of the base film, the molecular orientation axis direction is tilted from the running direction of the film. Even if the running direction of the film is processed to be aligned with the longitudinal or transverse direction of the packaging bag, the tear direction of the packaging bag will be tilted toward the molecular orientation axis direction of the base film. It is not practical to completely avoid procuring base film using the widthwise ends of the film, and the degree of distortion tends to become even greater than before as the production speed of base film increases and the width of the film increases.

[0006] Therefore, attempts have been made to solve these problems by improving the polyolefin resin film that is laminated onto the substrate film.

[0007] Patent Document 1 discloses a film obtained by uniaxially stretching a polyolefin resin sheet containing a propylene-ethylene block copolymer and an ethylene-propylene copolymer in a heat seal layer at a stretching ratio of 3.0. However, the film has problems with haze, heat seal strength, tear strength, bag rupture resistance, and tear separation.

[0008] Furthermore, Patent Document 2 discloses a film obtained by uniaxially stretching a polyolefin resin sheet containing a propylene-ethylene block copolymer, an ethylene-propylene copolymer, and a propylene-butene copolymer. However, there is a problem with the visibility of the contents.

[0009] Furthermore, Patent Document 3 discloses a film obtained by uniaxially stretching a polyolefin resin sheet containing a propylene-ethylene random copolymer and an ethylene-butene copolymer at a stretch ratio of about 5. However, there are problems with bag formability and tear resistance.

[0010] Furthermore, Patent Documents 4 and 5 disclose films obtained by uniaxially stretching a polyolefin resin sheet containing a propylene-ethylene block copolymer, a propylene-ethylene random copolymer, or a propylene-ethylene-butene random copolymer and an ethylene-butene elastomer by 4 to 6 times its original size. However, these films have problems such as poor dimensional stability against heat, which causes the package to deform and lose its appearance due to heat applied during retort treatment, and they are prone to tearing at low temperatures.

[0011] Also, Patent Document 6 discloses a film obtained by uniaxially stretching a polyolefin resin sheet mainly composed of a propylene-ethylene block copolymer at a stretching ratio of about four times. However, when a four-side sealed bag manufactured from a laminate with a biaxially stretched polyamide film or the like is torn open from the notch, a problem occurs in which thread-like pieces of film separate from the heat-sealed edge (commonly known as whiskers). [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent No. 5790497 [Patent Document 2] Patent No. 5411935 [Patent Document 3] Japanese Patent Application Publication No. 2018-79583 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-141302 [Patent Document 5] Special Publication No. 2012-500307 [Patent Document 6] WO2019 / 123944A1 Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention aims to provide a polyolefin resin film that, even when laminated with a base film having a large distortion in the molecular orientation axis such as a biaxially oriented polyamide resin film, provides a packaging bag obtained from the laminate that has excellent transparency, heat sealability, straight cutability, ease of tearing, bag-making processability, and bag-breaking resistance, and is less likely to produce whiskers when opened.

[0014] As a result of intensive research into achieving this object, the present inventors have found that a packaging bag made from a polypropylene resin composition containing at least one elastomer selected from the group consisting of a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, a propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst, an ethylene-butene copolymer elastomer, and a propylene-butene copolymer elastomer and an ethylene-propylene copolymer elastomer, and that while the polymer molecules are oriented primarily in one direction by stretching, the heat shrinkage rates in each direction are reduced and the molecular chain orientation in the longitudinal direction is within a specific range, when laminated with a base film having a large distortion in the molecular orientation axis, such as a biaxially oriented polyamide resin film, has excellent transparency, heat sealability, straight cutability, ease of tearing, bag-making processability, and bag rupture resistance, and is less likely to produce whiskers when opened, thereby completing the present invention. That is, the present invention has the following aspects.

[0015] [1] A polyolefin resin film made of a polypropylene resin composition, wherein the polyolefin resin film contains, based on a total of 100 parts by weight of the polypropylene resin, 20 to 95 parts by weight of a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, 0 to 75 parts by weight of a propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst, and 5 to 15 parts by weight of at least one elastomer selected from the group consisting of an ethylene-butene copolymer elastomer, a propylene-butene copolymer elastomer, and an ethylene-propylene copolymer elastomer, wherein the polyolefin resin film has a heat shrinkage rate of 1 to 10% in the longitudinal direction or the width direction, whichever direction has the larger heat shrinkage rate, and wherein the orientation coefficient ΔNx in the x-axis direction calculated from the refractive index of the polyolefin resin film is 0.0130 to 0.0250.

[0016] [2] The polyolefin resin film according to [1], which has a multi-layer structure of at least two layers.

[0017] [3] The polyolefin resin film according to [1] or [2], wherein the haze of the polyolefin resin film is 3% or more and 35% or less.

[0018] [4] The polyolefin resin film according to any one of [1] to [3], wherein the tear strength in the direction of the larger heat shrinkage rate out of the longitudinal direction and the width direction of the polyolefin resin film is 0.7 N or less.

[0019] [5] The polyolefin resin film according to any one of [1] to [4], wherein the concentration of the antiblocking agent in the layer located on at least one side of the polyolefin resin film is 3000 ppm or less.

[0020] [6] A laminate of the polyolefin resin film according to any one of [1] to [5] and a biaxially oriented film made of at least one polymer selected from the group consisting of polyamide resin films, polyester resin films, and polypropylene resin films.

[0021] [7] The laminate described in [6], wherein the straight cutability in the longitudinal direction or width direction of the laminate, whichever direction has the greater thermal shrinkage rate, is 10 mm or less, and the tear strength in the longitudinal direction or width direction, whichever direction has the greater thermal shrinkage rate, is 1.2 N or less.

[0022] [8] A package comprising the laminate described in [6] or [7]. [Effects of the Invention]

[0023] The polyolefin resin film of the present invention has excellent transparency, heat sealing properties, straight cut properties, tearability, bag formability, and resistance to puncture, and is suitable for providing packages that are less likely to produce whiskers when opened.

[0024] The present invention will be described in detail below. (Propylene-α-olefin random copolymer) In the present invention, the propylene-α-olefin random copolymer may be a copolymer of propylene and at least one α-olefin other than propylene having 4 to 20 carbon atoms. Examples of such α-olefin monomers having 2 or 4 to 20 carbon atoms include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, and octene-1. Although not particularly limited, ethylene is preferred in terms of stretchability and low shrinkage. Two or more types of propylene-α-olefin random copolymers may be mixed and used as needed.

[0025] The lower limit of the melt flow rate (MFR) of the propylene-α-olefin random copolymer is preferably 0.6 g / 10 min, more preferably 1.0 g / 10 min, and even more preferably 1.2 g / 10 min. If it is 0.6 g / 10 min or higher, the uniformity of the film thickness is less likely to be impaired. The upper limit of the melt flow rate of the propylene-α-olefin random copolymer is preferably 12.0 g / 10 min, more preferably 9.0 g / 10 min, and even more preferably 8.0 g / 10 min.

[0026] The lower limit of the melting point of the propylene-α-olefin random copolymer is not particularly limited, but is preferably 115°C, more preferably 120°C. At 115°C or higher, heat resistance is likely to increase, and the inner surfaces of the bag are less likely to fuse together during retort treatment. The upper limit of the melting point of the propylene-α-olefin random copolymer is not particularly limited, but is preferably 155°C, more preferably 150°C. At 155°C or lower, low-temperature sealability is likely to be achieved.

[0027] The copolymerization ratio of the α-olefin component in the propylene-α-olefin random copolymer is preferably 1 to 15% by weight, more preferably 3 to 10% by weight, and the copolymerization ratio of the propylene component in the propylene-ethylene block copolymer is preferably 85 to 99% by weight, more preferably 90 to 97% by weight.

[0028] The present invention includes a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, which is due to the fact that it has been polymerized using a metallocene-based olefin polymerization catalyst. Propylene-α-olefin random copolymers containing metallocene-based olefin polymerization catalysts are characterized by a narrower molecular weight distribution and fewer components on the lower and higher molecular weight sides than the weight average molecular weight (measured as an index). It has been newly discovered that the use of propylene-α-olefin random copolymers containing metallocene-based olefin polymerization catalysts suppresses the occurrence of whiskers. Furthermore, they offer excellent transparency, flexibility, and strength. The metallocene olefin polymerization catalyst is a catalyst comprising (i) a transition metal compound of Group 4 of the periodic table containing a ligand having a cyclopentadienyl skeleton (a so-called metallocene compound), (ii) a co-catalyst capable of reacting with the metallocene compound to activate it to a stable ionic state, and, if necessary, (iii) an organoaluminum compound, and any known catalyst can be used. Among the propylene-α-olefin random copolymers containing metallocene-based olefin polymerization catalysts, the most suitable are propylene-ethylene random copolymers in which the main monomer is propylene and a certain amount of ethylene is copolymerized. In this paper, the random copolymers are named and described in order of the monomer composition ratio that makes up the random copolymer. The propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst is specifically, for example, a propylene-ethylene random copolymer having an ethylene content of 7% by weight (Wintec WFX4M manufactured by Japan Polypropylene, resin density 900 kg / m 3 , MFR 7.0 g / 10 min at 230 °C and 2.16 kg, melting point 125 °C, metallocene catalyst), propylene-ethylene random copolymer with an ethylene content of 7 wt% (Japan Polypropylene WFW4M, resin density 900 kg / m 3 , 230°C, MFR 7.0g / 10min at 2.16kg, melting point 136°C, metallocene catalyst).

[0029] In the present invention, in addition to the propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, a propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst can also be used. Among the propylene-α-olefin random copolymers B containing Ziegler-Natta olefin polymerization catalysts, the most suitable are propylene-ethylene random copolymers in which the main monomer is propylene and a certain amount of ethylene is copolymerized. In this paper, the random copolymers are named and described in order of the monomer composition ratio that makes up the copolymer.

[0030] Specific examples of propylene-α-olefin random copolymers containing a Ziegler-Natta olefin polymerization catalyst include a propylene-ethylene random copolymer having an ethylene content of 4% by weight (Sumitomo Noblen WF577PG manufactured by Sumitomo Chemical Co., Ltd., MFR 3.2 g / 10 min at 230°C and a load of 2.16 kg, melting point 142°C), and a propylene-ethylene-butene random copolymer having an ethylene content of 1% by weight and a butene content of 3.6% by weight (Sumitomo Noblen FL8115A manufactured by Sumitomo Chemical Co., Ltd., MFR 7.0 g / 10 min at 230°C and a load of 2.16 kg, melting point 148°C).

[0031] (copolymer elastomer) In the present invention, a copolymer elastomer is contained in order to improve the resistance to breakage of a packaging bag obtained using the film of the present invention when dropped. The copolymer elastomer in the present invention is preferably an olefin-based thermoplastic copolymer elastomer that exhibits rubber-like elasticity near room temperature and / or an olefin-based thermoplastic copolymer elastomer that exhibits relatively high Shore hardness and good transparency, and it is preferable to use in combination an olefin-based thermoplastic copolymer elastomer that exhibits rubber-like elasticity near room temperature and an olefin-based thermoplastic copolymer elastomer that exhibits relatively high Shore hardness and good transparency. By using these in combination, even if straight cuttability and ease of tearing are imparted, transparency, heat sealability and bag break resistance can easily be obtained.

[0032] The copolymer elastomer has a melt flow rate (MFR) of 0.2 to 5.0 g / 10 min at 230°C and a load of 2.16 kg, and a density of 820 to 930 kg / m 3 It is desirable to use one having a molecular weight distribution (Mw / Mn) of 1.3 to 6.0 as determined by the GPC method. If the melt flow rate (MFR) under a load of 2.16 kg is 0.2 g / 10 min or more, uniform mixing is facilitated and fisheyes are less likely to occur, and if it is 5.0 g / min or less, bag rupture resistance is also likely to be improved.

[0033] The intrinsic viscosity [η] of the copolymer elastomer is preferably 1.0 dl / g to 5.0 dl / g, and more preferably 1.2 dl / g to 3.0 dl / g, from the viewpoints of maintaining heat seal strength, impact strength, and bag drop strength. When the intrinsic viscosity [η] is 1.0 dl / g or more, uniform kneading is facilitated and fisheyes are less likely to occur. When the intrinsic viscosity [η] is 5.0 dl / g or less, bag breakage resistance and heat seal strength can be easily improved.

[0034] An olefin-based thermoplastic copolymer elastomer that exhibits rubber-like elasticity at around room temperature is an ethylene-butene copolymer elastomer, which is an amorphous or low-crystalline elastomer obtained by copolymerizing ethylene and butene.

[0035] The copolymerization ratio of the ethylene component in the ethylene-propylene copolymer elastomer is preferably 55 to 85% by weight, more preferably 60 to 80% by weight, and the copolymerization ratio of the butene component in the ethylene-butene copolymer elastomer is preferably 15 to 45% by weight, more preferably 20 to 40% by weight. Specifically, the ethylene-butene copolymer elastomer has a butene content of 22% by weight, a melting point of 55°C, and a density of 870 kg / m 3 ethylene-butene copolymer elastomer (Tafmer A4070S manufactured by Mitsui Chemicals, Inc.) with a MFR (230°C, 2.16 kg) of 6.7 g / 10 min;

[0036] Among elastomers, propylene-butene copolymer elastomers, which are crystalline elastomers obtained by copolymerizing propylene and butene, are known as olefin-based thermoplastic copolymer elastomers that exhibit relatively high Shore hardness and good transparency. Specifically, the propylene-butene copolymer elastomer has a butene content of 20% by weight, a melting point of 83°C, and a density of 870 kg / m 3 An example of such a polymer is a propylene-butene copolymer elastomer (Tafmer XM7080 manufactured by Mitsui Chemicals, Inc.) having a MFR (230°C, 2.16 kg) of 7.0 g / 10 min.

[0037] (additives) The polyolefin resin composition of the present invention may contain an antiblocking agent. Although one type of antiblocking agent may be used, blending two or more types of inorganic particles with different particle sizes and shapes can form complex protrusions even on the unevenness of the film surface, thereby achieving a more advanced antiblocking effect. The antiblocking agent to be added is not particularly limited, but inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, and organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene can be added. In the case of a multi-layer structure of two or more layers, it may be added to all layers, but if there are irregularities on the surface of the layer on which the biaxially oriented film is laminated, this may result in a poor appearance of the laminated film, so it is preferable to add it only to the layer on which the films are heat-sealed together. The layer on which the biaxially oriented film is laminated is called the laminating layer, and its surface is called the laminating surface. The layer on which the films are heat-sealed together is called the heat-sealing layer, and its surface is called the heat-sealing surface. The amount of the antiblocking agent added is preferably 3000 ppm or less, more preferably 2500 ppm or less, based on the polyolefin resin composition of the layer to which it is added. By setting the amount to 3000 ppm or less, it is possible to reduce the falling off of the antiblocking agent.

[0038] The polyolefin resin composition of the present invention may contain an organic lubricant. This improves the lubrication and anti-blocking effect of the laminated film, and improves the film's handling properties. The reason for this is believed to be that the organic lubricant bleeds out and is present on the film surface, thereby exerting its lubricating and release effects. It is preferable to add an organic lubricant having a melting point above room temperature, and examples of the organic lubricant include fatty acid amides and fatty acid esters. Specific examples include oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, ethylene bisoleic acid amide, etc. These may be used alone, but it is preferable to use two or more of them in combination, since this allows the lubricity and anti-blocking effects to be maintained even under harsh environments.

[0039] The polyolefin resin composition of the present invention may contain an appropriate amount of an antioxidant, an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, an inorganic filler, and the like in any layer, as needed, within the scope of not impairing the object of the present invention. Antioxidants include a combination of phenolic and phosphite antioxidants, or a single compound having both phenolic and phosphite skeletons in one molecule. Neutralizing agents include calcium stearate.

[0040] (Polyolefin resin film) The polyolefin resin film of the present invention may be a single layer or may be composed of two or more layers, for example, a three-layer structure of a heat seal layer / laminate layer or a heat seal layer / intermediate layer / laminate layer, and each layer may be composed of multiple layers.

[0041] The heat seal layer is a layer located on the outermost surface side of the polyolefin resin film, and a package can be produced by placing the two surfaces of the heat seal layer face to face and thermocompressing them together. The layer located on the outermost surface opposite to the heat seal layer is a laminate layer, which can be laminated by being stuck to a base film such as a polyester film or a polyamide film. In the case of a three-layer structure of heat seal layer / intermediate layer / laminate layer, the end portion of the film product of the present invention or the film itself can be recovered and re-pelletized to be used as the raw material for the intermediate layer, thereby reducing the cost of the film product without impairing properties such as tearability, heat seal strength, and bag rupture resistance.

[0042] (Propylene-α-olefin random copolymer) In each layer of the polyolefin resin film of the present invention, the propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst is contained in an amount ranging from 20 to 95 parts by weight per 100 parts by weight of polyolefin resin in total. When the propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst is 25 parts by weight or more, the occurrence of whiskers is easily suppressed, and when it is 95 parts by weight or less, excellent resistance to bag rupture is achieved. A range of from 25 to 90 parts by weight is preferred. In each layer of the polyolefin resin film of the present invention, the propylene-α-olefin random copolymer containing a Ziegler-Natta olefin polymerization catalyst is contained in an amount of 0 to 75 parts by weight per 100 parts by weight of the polyolefin resin in total. When the propylene-α-olefin random copolymer containing a Ziegler-Natta olefin polymerization catalyst is 75 parts by weight or less, the occurrence of whiskers is easily suppressed.

[0043] (copolymer elastomer) Each layer of the polyolefin resin film of the present invention contains 5 to 15 parts by weight of at least one elastomer selected from the group consisting of ethylene-propylene copolymer elastomer, propylene-butene copolymer elastomer, and ethylene-butene copolymer elastomer, per 100 parts by weight of polypropylene resin in total. 5 parts by weight or more provides excellent bag-breaking resistance, while 15 parts by weight or less provides excellent bag-formability. A range of 7 to 13 parts by weight is preferred.

[0044] The polyolefin resin film of the present invention has a sea-island structure consisting of a matrix polymer and domains, which allows it to exhibit good bag-rupture resistance. The matrix polymer is mainly composed of the propylene-based portion of a propylene-α-olefin random copolymer, and the domains are mainly composed of the ethylene-based portion of a copolymer elastomer.

[0045] (Method of manufacturing polyolefin resin film) The polyolefin resin film of the present invention can be formed using, for example, an inflation method or a T-die method, but the T-die method is preferred for its enhanced transparency and ease of drafting. While the inflation method uses air as the cooling medium, the T-die method uses a cooling roll, making it an advantageous production method for increasing the cooling rate of the unstretched sheet. Increasing the cooling rate not only suppresses crystallization of the unstretched sheet, but also provides the advantage of easily controlling the load applied to stretching in the subsequent process. For these reasons, molding using the T-die method is more preferable.

[0046] The lower limit of the cooling roll temperature when the molten raw resin is cast to obtain a non-oriented sheet is preferably 15°C, more preferably 20°C. If the temperature is lower than the above, condensation occurs on the cooling roll, resulting in insufficient adhesion between the unstretched sheet and the cooling roll, which may cause thickness defects. The upper limit of the cooling roll is preferably 50°C, more preferably 40°C. If the temperature is 50°C or lower, the transparency of the polyolefin resin film is less likely to deteriorate.

[0047] The non-oriented sheet can be stretched by, for example, inflation, tenter transverse stretching, or roll longitudinal stretching, but roll longitudinal stretching is preferred because of ease of orientation control. The term "longitudinal stretching" as used herein refers to the direction in which the film flows from the step of casting the raw resin composition to the step of winding up the stretched film, and the term "transverse direction" refers to the direction perpendicular to the flow direction.

[0048] By stretching a non-oriented sheet under appropriate conditions, straight cut properties are achieved because the molecular chains are regularly aligned in the stretching direction. The lower limit of the stretching ratio is preferably 3.0 times. If the stretching ratio is 3.0 times or more, the tear strength in the stretching direction is unlikely to increase, and straight cuttability is easily obtained. It is more preferably 3.5 times, and even more preferably 3.8 times. The upper limit of the stretching ratio is preferably 5.5 times. At 5.5 times or less, excessive orientation is unlikely to proceed and the thermal shrinkage in the longitudinal direction is unlikely to increase. The upper limit is more preferably 5.0 times, and even more preferably 4.5 times.

[0049] The lower limit of the stretching roll temperature is preferably 80° C. If the temperature is 80° C. or higher, the stretching stress applied to the film does not become too high, and the thermal shrinkage rate in the longitudinal direction is unlikely to become large. It is more preferably 90° C. The upper limit of the stretching roll temperature is preferably 140°C. If the temperature is 140°C or lower, the stretching stress applied to the film will not be too low, and the thermal shrinkage rate of the film in the longitudinal direction will not be too low, and the film will not easily fuse to the stretching roll. The upper limit is more preferably 130°C, even more preferably 125°C, and particularly preferably 115°C.

[0050] It is preferable to bring the unstretched sheet into contact with a preheat roll to raise the sheet temperature before introducing it into the stretching step. The lower limit of the preheating roll temperature when stretching a non-oriented sheet is preferably 80°C, more preferably 90°C. If the temperature is 80°C or higher, the stretching stress does not become too high, and thickness fluctuation is unlikely to worsen. The upper limit of the preheating roll temperature is preferably 140°C, more preferably 130°C, and even more preferably 125°C. If the temperature is 140°C or lower, the film is unlikely to stick to the roll, and film thickness fluctuation is unlikely to increase.

[0051] The polyolefin resin film that has been stretched is preferably annealed to suppress thermal shrinkage. Annealing methods include roll heating and tentering, but the roll heating method is preferred because of the simplicity of the equipment and ease of maintenance. Annealing reduces the internal stress of the film, thereby suppressing its thermal shrinkage, and therefore does not sacrifice the longitudinal heat shrinkage rate or heat seal strength, as compared with the conventional method of simply increasing the stretch ratio to improve tearability. However, although annealing may have an adverse effect on properties other than the longitudinal heat shrinkage rate and heat seal strength, the use of a copolymer elastomer in combination with the present invention can suppress adverse effects on bag rupture resistance and the like. The lower limit of the annealing temperature is preferably 80°C. If the temperature is 80°C or higher, the thermal shrinkage rate in the longitudinal direction is unlikely to increase, the tear strength is likely to increase, and the finish of the packaging bag after bag making or retorting is unlikely to deteriorate. 100°C is more preferable, and 110°C is particularly preferable. The upper limit of the annealing temperature is preferably 140°C. A higher annealing temperature tends to reduce the thermal shrinkage in the longitudinal direction, but if the annealing temperature exceeds this limit, the film thickness fluctuation may worsen or the film may fuse to the manufacturing equipment. A more preferred upper limit is 135°C.

[0052] In the annealing step, a relaxation step can be provided by gradually slowing down the film transport speed, for example, by reducing the rotation speed of the roll after heating. By providing the relaxation step, the thermal shrinkage rate of the produced polyolefin resin film in the longitudinal direction can be reduced. The upper limit of the relaxation rate in the relaxation step is preferably 10%, more preferably 8%. If it is 10% or less, the thermal shrinkage rate in the longitudinal direction does not become too small. The lower limit of the relaxation rate is preferably 1%, more preferably 3%. If it is 1% or more, the thermal shrinkage rate of the polyolefin resin film is unlikely to become high.

[0053] In the present invention, it is preferable to activate the surface of at least one side of the polyolefin resin film or the surface of the laminate layer by corona treatment or the like, as this improves the lamination strength with the substrate film.

[0054] (film thickness) The lower limit of the thickness of the polyolefin resin film of the present invention is preferably 20 μm, more preferably 30 μm, even more preferably 40 μm, and particularly preferably 50 μm. If the thickness is 20 μm or more, the film will be relatively thick compared to the thickness of the base film, so the straight cutability of the laminate is less likely to deteriorate, the film will have a firm feel and be easy to process, and impact resistance and bag tear resistance will be easily obtained. The upper limit of the film thickness is preferably 150 μm, more preferably 100 μm, and even more preferably 80 μm. If the thickness is 150 μm or less, the film will not be too firm and will be easy to process, and suitable packages will be easily produced.

[0055] The properties of polyolefin resin films are described below. (Longitudinal orientation coefficient) The longitudinal orientation coefficient ΔNx used in the present invention can be calculated by Equation 1. ΔNx=Nx-(Ny+Nz) / 2 (Equation 1) Nx: X-axis Directional refractive index Ny: X-axis Refractive index in the direction perpendicular to the surface direction Nz: Refractive index in the thickness direction The lower limit of the longitudinal orientation coefficient ΔNx of the polyolefin resin film of the present invention is preferably 0.0130, more preferably 0.0150, and even more preferably 0.0160. When it is 0.0130 or more, the straight cuttability of the package is easily obtained. The upper limit of the longitudinal orientation coefficient ΔNx is preferably 0.0250, more preferably 0.0220. When it is 0.0250 or less, the heat seal strength is less likely to decrease.

[0056] (Thermal shrinkage rate) The upper limit of the larger heat shrinkage rate at 120°C in the longitudinal direction or width direction of the polyolefin resin film of the present invention is 10%. If it is 10% or less, the tear strength will be low and at the same time, shrinkage during heat sealing or retorting of the package will be large, resulting in excellent appearance of the package. It is preferably 8%, more preferably 7%, even more preferably 6%, and particularly preferably 5%. The lower limit of the larger heat shrinkage rate at 120°C in the longitudinal or transverse direction of the polyolefin resin film of the present invention is 1%. If it is 1% or more, the tear strength tends to be low. It is preferably 2%.

[0057] To achieve straight cutability, the lower limit of the orientation coefficient ΔNx in the X-axis direction needs to be 0.0130, but whisker formation is less likely to occur if the upper limit of the heat shrinkage rate at 120°C of the larger of the longitudinal and transverse directions is 10%. The reason for this is that when the film is heat-melted by heat sealing, orientation is less likely to remain in the sealed area or sealed edge, and the film laminated to the base film is restrained by the base film during heat sealing and is therefore less likely to shrink. This is thought to be because force is applied to the film, making it difficult to re-orient the film. The upper limit of the heat shrinkage rate of the polyolefin resin film of the present invention in the direction perpendicular to the direction in which the larger heat shrinkage rate is at 120°C, either the longitudinal or width direction, is 1%. If it is 1% or less, the tear strength in the longitudinal direction is likely to be low, making it easier to achieve straight cuttability. It is preferably 0.5%. The lower limit of the heat shrinkage rate of the polyolefin resin film of the present invention in the direction perpendicular to the direction in which the larger heat shrinkage rate is at 120°C, either the longitudinal or width direction, is -5%. If it is -5% or more, elongation may occur during heat sealing, which may deteriorate the appearance of the package. It is preferably -3%.

[0058] (tear strength) The upper limit of the tear strength in the longitudinal direction or width direction of the polyolefin resin film of the present invention, whichever direction has the larger heat shrinkage rate, is preferably 0.70 N, preferably 0.50 N, more preferably 0.45 N, and even more preferably 0.40 N. If the tear strength is 0.70 N or less, the laminate film is easily torn. The lower limit of the tear strength of the polyolefin resin film of the present invention in the longitudinal direction or the width direction, whichever direction has the larger heat shrinkage rate, is preferably 0.10 N. When the tear strength is 0.10 N or more, bag rupture resistance is easily obtained, and more preferably 0.20 N.

[0059] (Hayes) The lower limit of the haze of the polyolefin resin film of the present invention is preferably 3.0%, more preferably 5.0%. If it is 3.0% or more, the film surface is not extremely uneven, so blocking of the inner surface of the package is unlikely to occur. The upper limit of the haze is preferably 35.0%, more preferably 20.0%, even more preferably 15.0%, even more preferably 10%, and most preferably 8%. If it is 35.0% or less, visibility of the package is easily obtained.

[0060] (Puncture strength) The lower limit of the puncture strength of the polyolefin resin film of the present invention is preferably 3 N, more preferably 4 N / μm, and even more preferably 5 N. If it is 3 N or more, pinholes are less likely to occur when a protrusion hits the package. The upper limit of the puncture strength is preferably 10 N. If it is 10 N or less, the film will not feel too stiff, making it easy to handle when made into a film or laminate.

[0061] (Piercing strength) The lower limit of the puncture strength per μm of the polyolefin resin film of the present invention is preferably 0.05 N / μm, more preferably 0.09 N / μm. If it is 0.05 N / μm or more, pinholes are less likely to occur when the protrusions hit the package. The upper limit of the puncture strength is preferably 1.0 N / μm, more preferably 0.8 N / μm, and even more preferably 0.5 N / μm. If it is 1.0 μm / μm or less, the film will not feel too stiff, making it easy to handle when made into a film or laminate.

[0062] (Accelerated Blocking Strength) The lower limit of the accelerated blocking strength of the polyolefin resin film of the present invention is preferably 20 mN / 70 mm, more preferably 30 mN / 70 mm, even more preferably 100 mN, still more preferably 200 mN, and particularly preferably 250 mN. If it is 20 mN / 7 mm or more, the film tends to have a firm feel. The upper limit of the accelerated blocking strength is preferably 600 mN / 70 mm, more preferably 500 mN / 70 mm, even more preferably 400 mN / 70 mm, and even more preferably 300 mN. If it is 600 mN / 70 mm or less, blocking is less likely to occur on the inner surface of the package.

[0063] (wet tension) The lower limit of the wet tension of the surface of the polyolefin resin film of the present invention to be laminated with at least one film selected from the group consisting of polyamide resin films, polyester resin films, and polypropylene resin films is preferably 30 mN / m, more preferably 35 mN / m. If it is 30 mN / m or more, the laminate strength is less likely to decrease. The upper limit of the wet tension is preferably 55 mN / m, more preferably 50 mN / m. If it is 55 mN / m or less, blocking between films is less likely to occur when the polyolefin resin film is wound into a roll.

[0064] (Structure of laminate and manufacturing method) The laminate using the polyolefin resin film of the present invention is a laminate using the polyolefin resin film as a sealant and at least one film selected from the group consisting of polyamide resin film, polyester resin film, and polypropylene resin film. Furthermore, these substrate films may be coated or vapor-deposited using known techniques to impart adhesiveness or barrier properties, or may be further laminated with aluminum foil. Specific examples include biaxially oriented PET film / aluminum foil / sealant, biaxially oriented PET film / biaxially oriented nylon film / sealant, biaxially oriented nylon film / sealant, biaxially oriented polypropylene film / sealant, and biaxially oriented PET film / biaxially oriented nylon film / aluminum foil / sealant. Among these, biaxially oriented nylon films suffer from significantly poor straight-cutting properties when conventional sealants are used, but by using the polyolefin resin film of the present invention as a sealant, laminates with good straight-cutting properties can be produced in any configuration. As the lamination method, known methods such as dry lamination and extrusion lamination can be used, but any lamination method can produce a laminate with good straight cutability.

[0065] The properties of the laminate will now be described. (Piercing strength) The lower limit of the puncture strength of the laminate of the present invention before retort is preferably 10 N, more preferably 15 N, and even more preferably 18 N. If it is 10 N or more, pinholes are less likely to occur when the protrusions come into contact with the package. The upper limit of the puncture strength is preferably 45.0 N, more preferably 30.0 N, and even more preferably 25.0 N. If it is 45.0 N or less, the laminate will not be too stiff and will be easy to handle.

[0066] (tear strength) The upper limit of the tear strength of the laminate of the present invention in the longitudinal direction or width direction, whichever direction has the larger heat shrinkage rate, is preferably 1.2 N. If it is 1.2 N or less, the laminate is easily torn. It is more preferably 1.0 N, even more preferably 0.8 N, and even more preferably 0.5 N.

[0067] (Straight cutting ability) The straight cuttability refers to the ability of a laminate film (laminate) to tear straight in one direction when torn. Measurement was performed as follows. In this example, the film was stretched in the longitudinal direction, so the thermal shrinkage rate was high in the longitudinal direction, and the one direction was the longitudinal direction. Therefore, the straight cuttability was evaluated only in the longitudinal direction. The laminate film was cut into strips measuring 150 mm in the longitudinal direction and 60 mm in the width direction perpendicular to the longitudinal direction, and a 30 mm incision was made along the longitudinal direction from the center of the short edge. The sample was torn in accordance with JIS K7128-1:1998. At the point where the sample had been torn 120 mm in the longitudinal direction, excluding the 30 mm incision, the distance traveled perpendicular to the longitudinal direction (width direction) was measured and the absolute value was recorded. Measurements were performed in triplicate for both cases, with the right-hand piece clamped in the upper grip and the left-hand piece clamped in the upper grip, and the average value for each was calculated. The larger of the measurement results for the right and left sides was used.

[0068] (Straight cutting ability) The upper limit of the straight cuttability of the laminate of the present invention is preferably 10 mm, more preferably 9 mm, and even more preferably 7 mm. If it is 10 mm or less, the package is less likely to tear apart. The lower limit may be 1 mm.

[0069] (Tearful farewell) The upper limit of tearing of the laminate of the present invention is preferably 12 mm, more preferably 8 mm, even more preferably 5 mm, and even more preferably 4 mm. If it is 12 mm or less, the contents are less likely to spill when the package is torn. The lower limit may be 1 mm.

[0070] (beard incidence) A laminate film of the polyolefin resin film and base film of the invention was heat-sealed with the heat-seal films facing each other to create a four-sided sealed bag with internal dimensions of 120 mm in the longitudinal direction and 170 mm perpendicular to the longitudinal direction (width direction). A notch was made in the edge of the four-sided sealed bag, and it was torn by hand in the longitudinal direction. The whisker occurrence rate, calculated from the number of times thread-like film fragments (whiskers) appeared and the number of times it was torn, is preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, particularly preferably 16% or less, and most preferably 10% or less. The lower limit may be 1%. The laminate film was prepared by dry laminating the polyolefin resin film of the present invention and a substrate film (Toyobo biaxially oriented nylon film, N1102, 15 μm thick, 22° orientation angle relative to the longitudinal direction) using an ester-based adhesive obtained by mixing 33.6 parts by mass of an ester-based dry laminating adhesive (Toyo-Morton, TM569), 4.0 parts by mass of a curing agent (Toyo-Morton, CAT10L), and 62.4 parts by mass of ethyl acetate, so that the adhesive coating amount was 3.0 g / m2. The laminated film was kept at 40°C and aged for 3 days to obtain a laminate film.

[0071] (Finished bag) If the film undergoes heat shrinkage during the process of producing a package while heat-sealing the laminate, the heat-sealed area may become wrinkled or the package may have poor dimensions. When a four-side sealed bag is produced, it is preferable that the heat-sealed area is not wrinkled, and it is more preferable that the heat-sealed area is not wavy. If wrinkles occur in the heat-sealed area, the appearance of the package may be impaired.

[0072] (retort shrinkage rate) The upper limit of the retort shrinkage of the laminate of the present invention is preferably 5%. If it exceeds this limit, the appearance of the package after retort may deteriorate. It is more preferably 4%. The lower limit of the retort shrinkage in one direction is -5%. If it is less than this limit, the elongation after retort may be too great, which may cause the bag to break. It is more preferably -2%, and even more preferably 0%.

[0073] (Heat seal strength) The lower limit of the heat seal strength of the laminate of the present invention before retort is preferably 20 N / 15 mm, more preferably 35 N / 15 mm, and even more preferably 40 N / 15 mm. When it is 20 N / 15 mm or more, bag rupture resistance is easily obtained. A heat seal strength of 60 N / 15 mm is sufficient.

[0074] (Heat seal strength) The lower limit of the heat seal strength of the laminate of the present invention before retort is preferably 35 N / 15 mm, more preferably 40 N / 15 mm. If it is less than this, the bag rupture resistance may deteriorate. The heat seal strength preferably remains at 35 N / 15 mm or more even after retort treatment at 121°C for 30 minutes. The upper limit of the heat seal strength is preferably 60 N / 15 mm. To exceed this limit, it may be necessary to increase the thickness of the film, which may result in higher costs.

[0075] (packaging) The laminate, which is arranged to enclose the contents, such as foodstuffs, for the purpose of protecting the contents from natural dust, gases, and the like, is called a package. Packages are manufactured by cutting out the laminate, bonding the inner surfaces together using a heated heat seal bar or ultrasonic sealer, and forming them into a bag. A commonly used example is a four-sided sealed bag, in which two rectangular laminates are stacked with the sealant side facing inward and the four sides are heat-sealed. The contents may be foodstuffs, but may also be other products such as daily necessities, and the shape of the package may be a shape other than rectangular, such as a stand-up pouch or pillowcase. Furthermore, packaging that can withstand the heat of thermal sterilization using hot water whose boiling point has been raised to 100°C or higher by pressurization or other methods is called a retort packaging, and films intended to provide such packaging are called retort films.

[0076] (Bag resistance) A four-side sealed bag made from the laminate of the present invention is dropped and repeatedly dropped until the bag breaks, and the number of repeated drops is measured. From a practical standpoint, it is preferable that the number of drops at which 50% of the bags remain unbroken is 5 or more, more preferably 10 or more, even more preferably 12 or more, and even more preferably 13 or more. [Example]

[0077] The present invention will be described in detail below with reference to examples, but is not limited to these. The properties obtained in each example were measured and evaluated by the following methods. In the evaluation, the flow direction of the film in the film production process was defined as the longitudinal direction, and the direction perpendicular to the flow direction was defined as the width direction.

[0078] (1) Resin density The density was evaluated in accordance with JIS K7112:1999 D method (density gradient tube). N=3 measurements were taken and the average value was calculated.

[0079] (2) Melt flow rate (MFR) Measurements were carried out in accordance with JIS K-7210-1 at 230°C and a load of 2.16 kg. N=3 measurements were taken, and the average value was calculated.

[0080] (3) Hayes Haze was measured according to JIS K 7136. Measurements were made on the polyolefin resin film before lamination (N=3), and the average value was calculated.

[0081] (4) Tear strength The tear strength was measured in accordance with JIS K7128-1:1998. The polyolefin resin film before lamination and the laminate were evaluated. Measurements were made in the longitudinal direction and width direction with N=3, and the average value was calculated.

[0082] (5)Piercing strength The puncture strength of polyolefin resin films and laminates was measured at 23°C in accordance with "2. Testing Methods for Strength, etc." in "Specifications and Standards for Foods, Food Additives, etc., Part 3: Apparatus and Containers / Packaging" (Ministry of Health and Welfare Notification No. 20, 1982) under the Food Sanitation Act. A needle with a tip diameter of 0.7 mm was pierced into the film at a puncture speed of 50 mm / min, and the strength at which the needle penetrated the film was measured. The obtained measurement value was divided by the film thickness to calculate the puncture strength [N / μm] per 1 μm of film. N=3 measurements were made, and the average value was calculated.

[0083] (6) The orientation coefficient of the larger heat shrinkage rate at 120°C in the longitudinal direction or the transverse direction, and the plane orientation coefficient The refractive index was evaluated in accordance with JIS K 0062:1999, a method for measuring the refractive index of chemical products. N=3 measurements were performed, and the average value was calculated. The direction of the larger thermal shrinkage at 120°C, either the longitudinal or transverse direction, was defined as the X-axis direction, and the orientation coefficient ΔNx in the X-axis direction was calculated using Equation 1. ΔNx=Nx-(Ny+Nz) / 2 (Equation 1) Nx: X-axis Directional refractive index Ny: X-axis Refractive index in the direction perpendicular to the surface direction Nz: Refractive index in the thickness direction

[0084] (7) Heat shrinkage rate The film before lamination was cut into 120 mm squares. Marked lines were marked at 100 mm intervals in both the longitudinal and transverse directions. The sample was hung in an oven maintained at 120°C and heat-treated for 30 minutes. The distance between the marked lines was measured, and the thermal shrinkage rate was calculated according to the following formula 2. N=3 measurements were made, and the average value was calculated. Heat shrinkage rate = (gauge length before heat treatment - gage length after heat treatment) / gage length before heat treatment × 100 (%) (Equation 2)

[0085] (8) Accelerated blocking strength Polyolefin resin film was cut into a length of 148 mm in the longitudinal direction and 105 mm in the transverse direction. The heat-sealed surfaces were placed face-to-face and overlapped. After preheating for 30 minutes at 50°C, the film was sandwiched between 7.0 cm square aluminum plates maintained at 50°C. Using a Toyo Seiki Mini Test Press MP-SCH, the aluminum plate and the sample were pressed at 50°C and 100 kN and held for 15 minutes. The removed sample was cut into a 70 mm transverse direction. The overlapped sample was opened 30 mm, and a 3 mm diameter metal rod was inserted parallel to the transverse direction. The sample was mounted in a Shimadzu Autograph AG-I, and the load applied was measured while the metal rod was moved longitudinally at 200 mm / min. N=3 measurements were performed, and the average value was calculated.

[0086] (9) Straight cutting ability The straight cut property indicates the ability of the laminate to be torn straight in one direction when torn. Measurement was carried out in the following manner. In the examples and comparative examples, the straight cut property was exhibited in the stretching direction, so measurements were carried out in the stretching direction. The laminate was cut into strips measuring 150 mm in the stretching direction and 60 mm perpendicular to the measurement direction, and a 30 mm slit was made in the center of the short edge along the measurement direction. The sample was torn in accordance with JIS K7128-1:1998. At the point where the sample was torn 120 mm in the stretching direction, excluding the 30 mm slit, the distance traveled in the stretching direction and perpendicular to the stretching direction was measured and the absolute value was recorded. Measurements were performed with N=3 for both cases, where the right-hand piece was clamped in the upper grip and where the left-hand piece was clamped in the upper grip, and the average value for each was calculated. The larger of the measurement results for the right and left sides was used.

[0087] (10) Tearful Parting The laminate was heat-sealed with the heat-seal film facing each other to create a four-sided sealed bag with an internal dimension of 120 mm in the stretch direction and 170 mm perpendicular to the stretch direction. A notch was made at one end of the four-sided sealed bag, and it was torn by hand in the stretch direction. The cut was continued to the opposite end, and the deviation of the tear line between the film on the front and back sides of the bag was measured. Measurements were taken in both the right-hand side facing and left-hand side facing directions, with N=3 for each direction, and the average value was calculated. The larger measurement was used.

[0088] (11) Retort shrinkage rate The laminate film was cut into 120mm squares. Marked lines were marked at 100mm intervals in both the MD and TD directions. The film was retorted in hot water at 121°C for 30 minutes. The distance between the marks was measured, and the retort shrinkage was calculated according to the following formula. Measurements were performed on N=3 for each film, and the average value was calculated. Retort shrinkage rate = (gauge length before treatment - gage length after treatment) / gage length before treatment x 100 (%)

[0089] (12) Finished bag The polyolefin resin film sides of the laminates were overlapped and heat-sealed at 0.2 MPa for 1 second with a seal bar width of 10 mm and a heat seal temperature of 220°C to create a four-sided sealed bag with internal dimensions of 120 mm in the longitudinal direction and 170 mm in the width direction. The finished state of this four-sided sealed bag was visually inspected. ○: There is no distortion near the heat-sealed area, and the bag is perfectly rectangular. △: Little distortion near the heat-sealed area ×: There is a large distortion near the heat-sealed area, and the edges of the bag are wavy.

[0090] (13) Heat seal strength The heat-sealing conditions and strength measurement conditions were as follows. The polyolefin resin film sides of the laminates obtained in the Examples and Comparative Examples were overlapped and heat-sealed at 0.2 MPa for 1 second with a seal bar width of 10 mm and a heat-sealing temperature of 220°C, followed by cooling. Test pieces measuring 80 mm in the longitudinal direction and 15 mm in the transverse direction were cut from the films heat-sealed at each temperature. The peel strength of each test piece was measured when the heat-sealed portion was peeled off at a crosshead speed of 200 mm / min. The test machine used was an Instron Instruments Universal Testing Machine 5965. Measurements were performed three times for each test, and the average value was calculated.

[0091] (14) Sealing start temperature The seal initiation temperature is an item related to productivity when assuming continuous production using a bag making machine. Good bag making suitability means that sufficient sealing properties can be obtained within a temperature range where the base film does not shrink or break. The heat sealing temperature was evaluated as follows. In measuring the heat seal strength, the temperature of the heat seal bar was changed in 5°C increments, and the heat seal strength was measured for each test with N = 3. The heat seal strength was calculated by taking a weighted average of the heat seal temperature just before the heat seal strength exceeded 30 N and the heat seal temperature just after the heat seal strength exceeded 30 N.

[0092] (15) Beard incidence The laminated films were placed face-to-face with the heat-sealed films and heat-sealed to create a four-sided sealed bag with an internal dimension of 120 mm in the MD and 170 mm in the TD. A notch was made at the edge of the four-sided sealed bag, and it was torn by hand in the MD. The incidence rate was calculated from the number of times that thread-like film fragments (whiskers) appeared. Tests were conducted with n=100 in both the right-hand side and left-hand side facing directions, and the larger measurement value was used. Hair growth rate = number of hair growths / number of tears × 100 (%)

[0093] (16) Bag breakage resistance The laminate was cut out to create four-sided sealed bags with internal dimensions of 170 mm length and 120 mm width, each containing 300 ml of saturated saline solution. The heat-sealing conditions were a pressure of 0.2 MPa for 1 second, a seal bar width of 10 mm, and a heat-sealing temperature of 220°C. After bag production, the edges of the four-sided sealed bag were trimmed, leaving a heat-sealed width of 5 mm. The four-sided sealed bags were retorted at 115°C for 30 minutes. They were then left in a -5°C environment for 8 hours, and then dropped from a height of 1.0 m onto a flat concrete floor. The bags were repeatedly dropped until they broke, and the number of repeated drops was measured and classified as follows: 20 bags were produced for each level. ◎: 13 or more drops to reach a survival rate of 50% ○: The number of drops required to achieve a 50% survival rate is 10 to 12 times △: The number of drops required to achieve a 50% survival rate is between 5 and 9 times. ×: The number of drops that results in a survival rate of 50% is four or less.

[0094] (17) Orientation angle The orientation angle (°) of the base film was measured using a molecular orientation analyzer MOA-6004 manufactured by Oji Scientific Instruments Co., Ltd. A sample measuring 120 mm in the longitudinal direction and 100 mm in the transverse direction was cut out and placed on the measuring instrument, and the measured angle value was taken as the orientation angle. The longitudinal direction is 0°. Measurements were made with N=3, and the average value was calculated.

[0095] Example 1 (Polyolefin resin film) (Raw materials used) For the polypropylene-based resin film of Example 1, raw materials were prepared based on the resin compositions and ratios of each layer shown in Table 1 below. These raw materials were mixed uniformly to obtain a mixed raw material for producing a polyolefin-based resin film. 1) Raw material A: Propylene-ethylene random copolymer WFX4M (ethylene content 7% by weight, resin density 900 kg / m) manufactured by Japan Polypropylene 3 , 230℃, MFR 7.0g / 10min at 2.16kg, melting point 125℃, metallocene catalyst) 2) Raw material B: Japan Polypropylene propylene-ethylene random copolymer WFW4M (ethylene content 7% by weight, resin density 900 kg / m 3 , 230℃, MFR 7.0g / 10min at 2.16kg, melting point 136℃, metallocene catalyst) 3) Raw material C: Sumitomo Chemical Co., Ltd. propylene-ethylene random copolymer WF577PG (ethylene content 4% by weight, MFR 3.2 g / 10 min at 230°C and 2.16 kg, melting point 142°C, Ziegler-Natta catalyst) 4) Raw material D: Mitsui Chemicals propylene-butene copolymer elastomer resin XM7080 (butene content 20 wt%, melting point 83°C, MFR 6.7 g / 10 min at 230°C and 2.16 kg, density 870 g / m 3 ) 5) Raw material E: Mitsui Chemicals ethylene-butene copolymer elastomer resin A4070S (butene content 22% by weight, melting point 55°C, MFR 7.0g / 10min at 230°C and 2.16kg)

[0096] The total weight of the polypropylene resin mixture was 100 parts by weight, and 320 ppm of erucic acid amide was added as an organic lubricant, and silica with an average particle size of 4 μm was added as an inorganic anti-blocking agent so that the content in the resin composition was 2400 ppm by weight. These raw materials were mixed uniformly to obtain a mixed raw material for producing a polyolefin resin film.

[0097] (melt extrusion) The mixed raw materials for the intermediate layer were extruded in a three-stage single-screw extruder with a screw diameter of 90 mm, while the mixed raw materials for the laminate layer and heat-seal layer were extruded in three-stage single-screw extruders with diameters of 45 mm and 65 mm, respectively, in the order of laminate layer / intermediate layer / heat-seal layer. The extrusion was performed at an outlet temperature of 230°C, with a two-stage preland and a curved step shape to ensure uniform flow of the molten resin. The thickness ratios of the laminate layer / intermediate layer / heat-seal layer were 25% / 50% / 25%, respectively. The mixed raw materials were fed into the laminate layer, intermediate layer, and heat-seal layer in the same manner. (cooling) The molten resin sheet emerging from the die was cooled on a cooling roll at 21°C to obtain an unstretched polyolefin resin film with a thickness of 210 μm. When cooling on the cooling roll, both ends of the film on the cooling roll were fixed with air nozzles, and the entire width of the molten resin sheet was pressed against the cooling roll with an air knife. At the same time, a vacuum chamber was operated to prevent air from being drawn in between the molten resin sheet and the cooling roll. The air nozzles were installed in series on both ends in the direction of film travel. The die was surrounded by a sheet to prevent the molten resin sheet from being exposed to wind.

[0098] (preheat) The unstretched sheet was preheated by being guided through a group of heated rolls and brought into contact with the rolls. The temperature of the preheating rolls was 105°C. Multiple rolls were used to preheat both sides of the film. (longitudinal stretching) The unstretched sheet was introduced into a longitudinal stretching machine and stretched 3.5 times by the roll speed difference to a thickness of 60 μm. The stretching roll temperature was 105° C. (annealing treatment) The film was heat-treated at 130°C using an annealing roll. Both sides of the film were heat-treated using multiple rolls. (relaxation process) The speed of the roll placed next to the annealing roll was reduced by 5% as a relaxation rate relative to the annealing roll to relax the film.

[0099] (Corona treatment) One side of the film (the laminating side) was subjected to a corona treatment. (winding) The film was formed at a film forming speed of 20 m / min. The edge portions of the formed film were trimmed and wound into a roll.

[0100] (Creating a laminate) The polyolefin resin films obtained in the examples and comparative examples and a biaxially oriented nylon film (N1102, 15 μm thick, 22° orientation angle relative to the longitudinal direction) manufactured by Toyobo Co., Ltd. as a base film were coated with an ester adhesive obtained by mixing 33.6 parts by mass of a base agent (TM569 manufactured by Toyo-Morton Co., Ltd.), 4.0 parts by mass of a curing agent (CAT10L manufactured by Toyo-Morton Co., Ltd.), and 62.4 parts by mass of ethyl acetate at a coating amount of 3.0 g / m 2 The resulting film was wound up and kept at 40°C for 3 days to age the film, yielding a laminate.

[0101] (Examples 2 to 5) A 60 μm polyolefin resin film was obtained in the same manner as in Example 1, except that the raw materials shown in Table 1 were used, the thickness of the unstretched polyolefin resin film was 240 μm, and the longitudinal stretching ratio was 4.0 times. A laminate was obtained in the same manner as in Example 1.

[0102] (Comparative Example 1) A 60 μm polyolefin resin film was obtained in the same manner as in Example 1, except that the raw materials shown in Table 2 were used. A laminate was obtained in the same manner as in Example 1.

[0103] (Comparative Example 2) A 60 μm polyolefin resin film was obtained in the same manner as in Example 1, except that the raw materials shown in Table 2 were used, the thickness of the unstretched polyolefin resin film was 240 μm, and the longitudinal stretching ratio was 4.0 times. A laminate was obtained in the same manner as in Example 1.

[0104] (Comparative Example 3) In Example 1, a 60 μm polyolefin resin film was obtained in the same manner as in Example 1, except that the raw materials shown in Table 2 were used, the thickness of the unstretched polyolefin resin film was 150 μm, the longitudinal stretching ratio was 2.5 times, and the relaxation rate in the relaxation step was 3%. A laminate was obtained in the same manner as in Example 1.

[0105] Comparative Example 4 A 60 μm polyolefin resin film was obtained in the same manner as in Example 1, except that the raw materials shown in Table 2 were used, the thickness of the unstretched polyolefin resin film was 360 μm, and the longitudinal stretching ratio was 6.0 times. A laminate was obtained in the same manner as in Example 1.

[0106] (Comparative Example 5) In Example 1, a 60 μm polyolefin resin film was obtained in the same manner as in Example 1, except that the raw materials shown in Table 2 were used, the thickness of the unstretched polyolefin resin film was 150 μm, the longitudinal stretching ratio was 2.5 times, and the relaxation rate in the relaxation step was 3%. A laminate was obtained in the same manner as in Example 1.

[0107] (Comparative Example 6) A polyolefin resin film having a thickness of 60 μm was obtained in the same manner as in Example 1, except that the relaxation rate was set to 0%.

[0108] (Comparative Example 7) A polyolefin resin film having a thickness of 60 μm was obtained in the same manner as in Example 1, except that the annealing treatment was not performed and the relaxation rate was set to 0%.

[0109] (Comparative Example 8) A polyolefin resin film having a thickness of 60 μm was obtained in the same manner as in Example 2, except that the relaxation rate was set to 0%.

[0110] In Comparative Examples 1 and 2, the frequency of whisker formation was high because no metallocene-based ethylene-propylene random copolymer was used. In Comparative Examples 3 and 5, the stretching ratio was low and the orientation coefficient in the x-axis direction was low, so that the straight cuttability was poor. In Comparative Example 4, the stretching ratio was high and the orientation coefficient in the x-axis direction was high, so the heat shrinkage rate was high. In Comparative Examples 6 to 8, the relaxation rate after annealing was set to 0%, so the thermal shrinkage rate was high. The results are shown in Tables 1 and 2.

[0111] [Table 1]

[0112] [Table 2]

[0113] In Tables 1 and 2, the evaluation results marked as "Not measurable*" indicate that the film was torn in the stretching direction during the property evaluation, and no measurement value could be obtained. [Industrial Applicability]

[0114] The present invention can provide a package that is excellent in transparency, heat-sealing properties, bag-making properties, and tear-resistance, that can be easily torn without tearing, and that is less likely to produce whiskers when opened, thereby making a great contribution to industry.

Claims

1. A polyolefin resin film made of a polypropylene resin composition, wherein the polypropylene resin constituting the polypropylene resin composition is made of at least one elastomer selected from the group consisting of a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, a propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst, an ethylene-butene copolymer elastomer, and an ethylene-propylene copolymer elastomer, and the polyolefin resin composition contains 20 parts by weight or more and 95 parts by weight or less of the propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst and a Ziegler-Natta-based olefin polymerization catalyst in a total of 100 parts by weight of the polypropylene resin. a polyolefin-based resin film stretched in the longitudinal or width direction, the polyolefin-based resin film containing 0 to 75 parts by weight of a propylene-α-olefin random copolymer ...

2. A polyolefin resin film made of a polypropylene resin composition, wherein the polypropylene resin constituting the polypropylene resin composition comprises a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, a propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst, an ethylene-butene copolymer elastomer, and a propylene-butene copolymer elastomer, and the polyolefin resin film contains 20 parts by weight or more and 95 parts by weight or less of the propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst and the propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst in a total of 100 parts by weight of the polypropylene resin. a polyolefin-based resin film stretched in the longitudinal or width direction, the polyolefin-based resin film containing 0 to 75 parts by weight of a propylene-α-olefin random copolymer including α-olefin copolymer and 5 to 15 parts by weight in total of an ethylene-butene copolymer elastomer and a propylene-butene copolymer elastomer; the polyolefin-based resin film having a heat shrinkage rate of 1 to 8% in the longitudinal or width direction of the polyolefin-based resin film, the heat shrinkage rate being greater than or equal to 1% and the heat shrinkage rate being greater than or equal to 8%; and the orientation coefficient ΔNx in the x-axis direction calculated from the refractive index of the polyolefin-based resin film being greater than or equal to 0.0150 and less than or equal to 0.0220 when the x-axis direction is the longitudinal or width direction of the polyolefin-based resin film.

3. A polyolefin resin film made of a polypropylene resin composition, the film having a multi-layer structure of at least two layers, in which the polypropylene resin constituting the polypropylene resin composition in each of the multi-layer structures is at least one elastomer selected from the group consisting of a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, a propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst, an ethylene-butene copolymer elastomer, and an ethylene-propylene copolymer elastomer, and the propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst accounts for 20% of 100 parts by weight of the polypropylene resin in total. a polyolefin resin film containing from 0 to 75 parts by weight of a propylene-α-olefin random copolymer containing a Ziegler-Natta olefin polymerization catalyst; and from 5 to 15 parts by weight of at least one elastomer selected from the group consisting of an ethylene-butene copolymer elastomer and an ethylene-propylene copolymer elastomer, wherein the polyolefin resin film has a heat shrinkage rate of from 1 to 8% in the longitudinal direction or the width direction whichever direction has the larger heat shrinkage rate, and wherein the orientation coefficient ΔNx in the x-axis direction calculated from the refractive index of the polyolefin resin film is from 0.0150 to 0.0220 when the x-axis direction is the longitudinal direction or the width direction which has the larger heat shrinkage rate.

4. A polyolefin resin film made of a polypropylene resin composition, the film having a multi-layer structure of at least two layers, in each of the multi-layer structures, the polypropylene resins constituting the polypropylene resin composition are made of a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, a propylene-α-olefin random copolymer containing a Ziegler-Natta-based olefin polymerization catalyst, an ethylene-butene copolymer elastomer, and a propylene-butene copolymer elastomer, and the polypropylene resin is a propylene-α-olefin random copolymer containing a metallocene-based olefin polymerization catalyst, in a total of 100 parts by weight of the polypropylene resin. a polyolefin resin film containing 20 to 95 parts by weight of a copolymer of 2,000 and 1,000 propylene-α-olefin random copolymers containing a Ziegler-Natta olefin polymerization catalyst; and 5 to 15 parts by weight in total of an ethylene-butene copolymer elastomer and a propylene-butene copolymer elastomer, wherein the polyolefin resin film has a heat shrinkage rate of 1 to 8% in the longitudinal direction or the width direction whichever direction has the larger heat shrinkage rate, and wherein the orientation coefficient ΔNx in the x-axis direction calculated from the refractive index of the polyolefin resin film is 0.0150 to 0.0220 when the x-axis direction is the longitudinal direction or the width direction whichever direction has the larger heat shrinkage rate.

5. 5. The polyolefin resin film according to claim 1, wherein the haze of the polyolefin resin film is 3% or more and 35% or less.

6. 5. The polyolefin resin film according to claim 1, wherein the polyolefin resin film has a tear strength of 0.7 N or less in the longitudinal direction or width direction in which the heat shrinkage rate is greater.

7. 3. The polyolefin resin film according to claim 1, wherein the polyolefin resin film has an antiblocking agent concentration of 3000 ppm or less.

8. 5. The polyolefin resin film according to claim 3, wherein the concentration of the antiblocking agent in a layer located on at least one side of the polyolefin resin film is 3,000 ppm or less.

9. A laminate of the polyolefin resin film according to any one of claims 1 to 4 and a biaxially oriented film made of at least one polymer selected from the group consisting of polyamide resin film, polyester resin film, and polypropylene resin film.

10. The laminate according to claim 9, wherein the straight cut ability in the longitudinal direction or width direction of the laminate, whichever direction has the larger heat shrinkage rate, is 10 mm or less, and the tear strength in the longitudinal direction or width direction, whichever direction has the larger heat shrinkage rate, is 1.2 N or less.

11. A package comprising the laminate according to claim 9.

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